Developmental candidate GHP-88310/EIDD-3608 with high tolerability and oral efficacy in measles and respiratory paramyxovirus models

Figures

• 

  Fig. 1.. SAR development of broad-spectrum GHP-class polymerase inhibitors. (A) Study schematic of multidose GHP-88309 tolerability and PK assessment. Ferrets received 14 oral doses of GHP-88309 at two different concentrations, administered twice daily. (B) Survival curves of animals from (A). (C) PK profile of GHP-88309 (50 mg/kg) in ferret plasma following 14 oral doses administered b.i.d. Exposure is specified. (D to F) Survival curves (D), body temperature (E), and clinical scores (F) of animals after single oral dose of GHP-88309. Body temperature scoring: 0, >38°C; 1, 37.5° to 37.9°C; 2, 37° to 37.4°C; 3, <37°C. Neurologic scoring: 0, explores objects, weasel war dance, intact reflexes; 1, decreased interest in exploring objects; 2, lethargic, and/or altered gait, and/or decreased reflexes; 3, obtunded, and/or seizures, and/or paralysis in one or more limbs. (G) Top-ranking GHP-88309 analogs. Dashed circles mark regions that QSAR models (23) have identified as most amenable to synthetic elaboration. (H) Evaluation of cellular viability of GHP compounds on Vero E6 cells. (I to K) Recombinant virus reporter-based dose response inhibition of HPIV3 (I), MeV (J), and CedV (K); n ≥ 3. (L)…

• 

  Fig. 2.. PK and efficacy evaluation of GHP-88309 analogs in rodents. (A) Study schematic. 129X1/SvJ mice were infected intranasally with 1.5 × 105 TCID50 units of recSeV. Compounds were administered orally b.i.d., starting 1 dpi and continuing through 8.5 dpi. (B to D) Survival curves (B), trachea (C), and lung (D) viral titers determined 5 dpi. (E) Study overview. Direct comparison of GHP-88309 and GHP-88310 efficacy conducted in cotton rats. Animals were intranasally infected with 1 × 106 TCID50 units of HPIV3 isolate 13J5. Oral dosing was initiated 12 hpi and continued b.i.d. (F and G) Trachea (F) and combined left and right cranial lungs (G) were collected 3.5 dpi and viral titers determined by plaque assay. (H) Study outline of single-dose PK and tissue distribution analysis in cotton rats, comparing 50 mg/kg doses of GHP-88309 and GHP-88310. (I and J) PK profiles of GHP-88309 and GHP-88310 in cotton rat plasma (I) and tissue concentrations of GHP-88309 and GHP-88310 measured 8 hours postdosing (J). Unpaired, two-tailed t test. Bars indicate the geometric means ± geometric SD. (K) Multidose GHP-88310 tolerability and PK study. Cotton rats received 14 oral doses, administered b.i.d.…

• 

  Fig. 3.. Single and multidose tolerability and PK of twice-daily GHP-88310 in ferrets. (A) Overview of single oral dose PK study of GHP-88309 and GHP-88310 in ferrets. (B) PK profile of GHP-88309 and GHP-88310 in ferret plasma. (C) Schematic of multidose tolerability and PK study of GHP-88309 and GHP-88310 at different concentrations. Ferrets received 14 oral doses, administered b.i.d. Cmax was measured daily in ferrets administered 500 and 1000 mg/kg GHP-88310. (D) Survival curves; data for the 150 mg/kg GHP-88309 group, originally shown in (Fig. 1 (A and B), are included for direct comparison. Log-rank (Mantel-Cox) test with median survival. (E) Cmax of GHP-88310 to monitor plasma build-up after doses 1, 2, 4, 6, 8, 10, 12, and 14. (F) PK profile of GHP-88310 in ferret plasma after 14 oral doses. (G) CBC analysis of ferret blood samples quantifying white blood cells (left), red blood cells (middle), and red blood cell width (right). Normal range for each parameter is shown in green shading. Left, middle: Symbols indicate the geometric means ± geometric SD. Right: Symbols represent means ± SD. Two-way ANOVA followed by Dunnett’s (comparisons to mock) post hoc multiple comparisons test.…

• 

  Fig. 4.. Therapeutic effect of GHP-88310 on CDV infection in ferrets. (A) Virus yield reduction of recCDV-5804p. Variable-slope four-parameter nonlinear regression modeling; n ≥ 3. Symbols indicate the geometric means ± geometric SD. (B) Overview of assessment of q.d. and b.i.d. GHP-88310 therapeutic potential. Ferrets were infected intranasally with 2 × 105 TCID50 units of recCDV-5804p. Oral administration of GHP-88310 began 3 days after infection and continued until 10 (150 mg/kg) or 21 (50 mg/kg) dpi. (C) Survival curves. Log-rank (Mantel-Cox) test with median survival. (D to F) PBMC-associated viremia (D), nasal lavage viral titers quantified by TCID50 assay (E), and lymphocyte counts (F) are shown. Normal range of lymphocytes is depicted by green shading. (G) Neutralizing antibody titers. In (D) to (F), symbols indicate individual animals and lines represent geometric means. Two-way ANOVA followed by Dunnett’s (comparisons to vehicle) post hoc multiple comparisons test. Created in BioRender. Plemper, R. (2026) https://BioRender.com/vwgtnw9. D, day; ns, not significant.

• 

  Fig. 5.. Functional and molecular profiling of GHP-88310. (A to C) Dose-response assays with recombinant virus variants or in a minigenome harboring mutations that mediate reduced susceptibility to GHP-88309. Shown are variable-slope four-parameter nonlinear regression curves for HPIV3 (A), SeV (B), and in a MeV minigenome (C). Fifty percent and 90% inhibitory concentrations against each compound are provided. Yellow highlights mark mutations that result in a ≥5-fold increase in EC50 and/or EC90 compared to the unmodified genetic parent virus. (D) In silico docking of GHP-88310. Ribbon representation of the MeV L-P structure (PDB: 9DUS), highlighting the predicted docking location (black spheres in red dashed box) of GHP-88310 (left). The RdRP and capping domains are colored in cyan and green, respectively. Ribbon representation of the top scoring docking pose conserved between GHP-88309 and GHP-88310 (middle). GHP-88310 docking pose is shown as gray sticks. Residues that have been shown to confer resistance to GHP-88309 are highlighted in red. Surface representation of the docking site of GHP-88310 showing the location of the docking pose between the capping and RdRP domains (right). In…

• 

  Fig. 6.. GHP-88310 efficacy in well-differentiated ALI HAE cultures. (A) Virus yield reduction of HPIV3 (clinical isolate 13J5) in undifferentiated NHBE cells (F3, n = 3). (B) Schematic of well-differentiated ALI HAE organoids. (C) Assessment of GHP-88310 cytotoxicity in organoids. TEER was measured before and after 48 hours of exposure to increasing concentrations of GHP-88310 in the basolateral chamber. Symbols represent individual biological measurements, and lines show medians. (D) Virus yield reduction assay of HPIV3 in organoids. Shed progeny virus was collected from the apical side of the transwells. Curves show variable-slope four-parameter nonlinear regression models, and symbols represent the geometric means ± geometric SD. (E) HPIV3 titers in infected organoids used for confocal imaging. (F) Confocal microscopy of organoids infected with HPIV3 at 2 dpi. Cells were stained with anti-HPIV3 HN (red), anti-ZO-1 [tight junctions (TJs); green], and Hoechst 34580 (nuclei; blue). Z-stacks of 100 to 150 0.22-μm slices with 63× oil objective. Scale bar, 10 μm. (G) Ex vivo PK-guided assessment of GHP-88310 efficacy against HPIV3 in organoids. The simulation recapitulates the PK profile of…